This invention relates to a lens holder driving device and, in particular, to an autofocus lens holder driving device for use in a compact camera.
Camera-equipped cellular mobile phones mount compact cameras therein. The compact camera is provided with an autofocus lens holder driving device. Previously, various autofocus lens holder driving devices have been proposed.
By way of illustration, Japanese Unexamined Patent Application Publication No. 2009-251031 (JP-A-2009-251031) (which will be also called Patent Document 1) discloses a lens driving device which is capable of decreasing a parts count and of miniaturizing. The lens driving device disclosed in Patent Document 1 comprises a lens holder in which a lens assembly can be mounted, a driving coil (a coil) fixed to the lens holder at outside circumstance thereof, a magnet opposite to the driving coil, an outer yoke including the magnet, an elastic member (an upper elastic member and a lower elastic member) for supporting the lens holder in a direction of an optical axis of the lens assembly shiftably, and a base disposed at a lower side of the lens holder. In Patent Document 1, the elastic member (the upper elastic member and the lower elastic member) is disposed in the inside of the outer yoke.
In addition, in the lens driving device disclosed in the above-mentioned Patent Document 1, each of the upper elastic member and the lower elastic member comprises an inner end portion mounted to the lens holder and an outer end portion mounted to the outer yoke. The above-mentioned Patent Document 1, as a second exemplary embodiment, comprises a spacer at a corner portion of the outer yoke as a holding member for holding the outer end portion of the upper elastic member.
The lens holder driving device disclosed in the above-mentioned Patent Document 1 further comprises an inner yoke (a back yoke) for fixing the outer end portion of the lower elastic member via a spacer. The inner yoke comprises an inner ring end portion mounted to an inner wall of an outer hollow cylindrical portion of the outer yoke at a lower end thereof and a plurality of vertical extending portions which extend in parallel with the optical axis vertically upwards at the inside of the inner ring end portion. The driving coil is disposed between the plurality of vertical extending portions of the inner yoke and the magnet.
In the above-mentioned lens driving device disclosed in Patent Document 1, the outer end portion of the upper elastic member is held and fixed to the corner portion of the inner wall of the outer yoke via the spacer. It is therefore difficult to easily mount the upper elastic member to the outer yoke and it is also difficult to position the upper elastic member to the outer yoke.
In addition, in the lens driving device disclosed in Patent Document 1, the inner yoke (the back yoke) is mounted to the inner wall of the outer hollow cylindrical portion of the outer yoke at the lower end thereof. It is therefore difficult to easily assemble the lens driving device.